This invention relates generally to medical devices, and more particularly, to endoluminal prostheses such as stent grafts and methods for treating branched vessels. The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, a vessel wall can weaken, resulting in an aneurysm, or it may develop a tear in one of the layers of the wall resulting in a dissection.
One common surgical intervention for weakened, aneurysmal or ruptured passageways or ducts involves the use of an endoluminal prosthesis to provide some or all of the functionality of the original, healthy passageway or duct and/or preserve any remaining vascular integrity by replacing a length of the existing passageway or duct wall that spans the site of failure or defect. Endoluminal prostheses may be of a unitary construction or may be comprised of multiple prosthetic segments. They also may be a single tubular device or a bifurcated branching device depending on the desired application or the particular portion of the vasculature being treated.
In many cases, the damaged or defective portion of the vasculature may include a branch vessel extending from a main vessel. Fenestrated and/or branched endoluminal prostheses are known for treating such branch vessels. In one example, an iliac branch device (IBD) may be placed in the common iliac artery (CIA). An iliac branch device generally consists of a main lumen which runs from the CIA to the external iliac artery (EIA) with a side branch extending from the main lumen and facing the internal iliac artery (IIA). The proximal end of the iliac branch device may connect directly to an AAA main body graft, or alternatively, the proximal end of the iliac branch device may be sealed to the AAA main body via an intermediate bridging limb.
Introduction of an iliac branch device and successful deployment thereof may often depend upon a favorable layout of the arteries. However, the anatomy of the vasculature may be unique from one patient population to the next and also among individual patients. Anatomical limitations may restrict the patient base which is able to receive a branched graft, such as an iliac branch device, the chief limitation being the length of the common iliac artery. In one example, branched stent grafts have been used to treat patients having common iliac arteries of a certain average length (e.g., the measured distance from the main aortic bifurcation to the ostium of the internal iliac artery), such as approximately 40 mm in length or greater. The common iliac artery must be of a certain minimum length in order for the iliac branch device to seat properly, such that the fenestration and/or side branch of the graft is adjacent the ostium of the IIA while the proximal end of the iliac branch device does not extend above the aortic bifurcation, for example. However, the length of the common iliac arteries among certain patient populations, particularly in Asia, may be on average shorter, down to 20 mm in length or even less, such that treatment with a standard length iliac branch device may be difficult.